Field induced quantum phase transition in the anisotropic Kondo necklace model

TL;DR

This paper investigates how magnetic fields influence quantum phase transitions in the anisotropic Kondo necklace model, revealing complex behaviors like destruction or induction of antiferromagnetism and reentrant phases.

Contribution

It extends previous zero-field studies to finite fields, analyzing the effects of anisotropy and g-factors on the quantum critical behavior in heavy fermion systems.

Findings

Identification of three distinct field-dependent behaviors of the phase transition.

Derivation of phase diagrams showing field-induced transitions.

Analysis of anisotropy and g-factor effects on critical fields.

Abstract

The anisotropic Kondo necklace model in 2D and 3D is treated as a genuine model for magnetic to Kondo singlet quantum phase transitions in the heavy fermion (HF) compounds. The variation of the quantum critical point (QCP) with anisotropy parameters has been investigated previously in the zero field case [1]. Here we extend the treatment to finite fields using a generalised bond operator representation including all triplet states. The variation of critical tc with external field H and the associated phase diagram is derived. The influence of anisotropies and the different g-factors for localised and itinerant spins on tc(H) is also investigated. It is found that three different types of behaviour may appear: (i) Destruction of antiferromangetism and appearance of a singlet state above a critical field. (ii) The inverese behaviour, namely field induced antiferromagnetism out of the Kondo singlet phase. (iii) Reentrance behaviour of the Kondo singlet phase as function of field strength.